Of the over 2k nukes Russia and U.S possess it's comical to think more than a dozen would even be needed.
Nukes today have about 2k-3k times more destruction power than Hiroshima and Nagasaki, and those
two bombs left about 100k dead and 100k injured. If Putin uses nukes in Ukraine there is no way he can control the fallout in fact it will harm Russia as well...not to mention sanctions and the economical impact for years to come which will set ruskis back 500 years.
I think putinka knows he can't touch nukes and i think that CIA knows that too, what they tell the public is another matter.